Plastic bobbins are utilized in ballasts for fluorescent lights and the like. One form of such a ballast is disclosed in U.S. patent application Ser. No. 257,538 filed Oct. 14, 1988, entitled "An Improved Ballast", the disclosure of which is incorporated herein by reference. The ballast of the co-pending application is formed of plastic and is molded through the use of one or more die parts having suitable cavities formed therein so that a bobbin is created including an elongated rectangular body member having a plurality of flanges and standoffs extending radially outwardly therefrom.
At at least one end of the bobbin, a series of flat metal terminals are mounted in receiving pockets formed in the bobbin. The terminals have tabs protruding therefrom upon which terminations from the coils are wound and joined by conductors to various other electrical connections. In order to retain the terminals in the receiving pockets of the bobbin, the edges of the terminal have a series of angular teeth punched therein which grip the plastic sides of the pocket to allow insertion of the terminal and retain the terminal in position.
The major problem with the terminals conventionally used, is in the gripping power of the teeth punched into the edges of the terminal. The transverse "leading" edge of the punched angular tooth is the gripping portion of the tooth, and contacts a wall of the bobbin pocket to prevent longitudinal movement of the terminal outwardly from the pocket. Because the teeth were conventionally formed of small tabs punched directly along the edges of the terminal, it was found that the "leading" edge would be formed slightly rounded by this punching action.
A rounded leading edge on the gripping tooth causes several problems. One problem is that the retention power of the tooth is greatly reduced because there is no sharp edge to grip the plastic side wall. A second problem is related to the first in that the reduction of retention power of the tooth requires the tooth to be bent at a more severe angle to increase the gripping power. A more severe angle increases the distortion of the bobbin pocket and increases the amount of force required to insert the terminal in the pocket. Both of these characteristics are clearly undesirable.
It is therefore a general object of the present invention to provide an improved terminal for a bobbin.
Another object of the present invention is to provide a terminal having teeth with a sharp leading edge for greater gripping power.
A further object of the present invention is to provide an improved terminal with increased gripping power but decreased insertion force and no distortion of the bobbin pocket, as compared to prior terminals.
Still another object of the present invention is to provide a method for forming teeth in a terminal which will produce a sharp leading edge on the tooth.
These and other objects of the present invention will be apparent to those skilled in the art.